Certain valve arrangements are known from the company brochure Sauer-Danfoss “PVSK module with integrated diverter valve and P-disconned function”, edition November 2002.
With machines and devices performing hydraulic functions, usually several consumers are present, each being controlled by a control valve. For example, in connection with a crane, there are several cylinders, which lift different sections of a jib, a rotary motor, with which the jib can be turned, and, if required, a further hydraulic function, with which a grab mounted at the end of the jib can be activated. Similar conditions exist with other devices with hydraulic functions, for example mobile working platforms, diggers, etc.
In this connection, the control valves are connected to a component group, which is supplied with pressurised hydraulic fluid via the high-pressure connection. The control valves can, for example, be proportional valves, which permits the flow of a predetermined volume flow of hydraulic fluid to the working connection and thus to the consumer in dependence of the position of a valve element.
The safety requirements in connection with the safety of devices and machines provided with hydraulic functions are relatively high. Particularly, it is endeavoured to avoid that people are hurt, when errors occur.
From the brochure mentioned above, it is therefore known to combine the control valves with a safety valve. This safety valve interrupts the supply of hydraulic fluid to the control valves, when no supply is desired. For example, the safety valve can be operated in such a manner that the control valves are cut off from the supply, when a vehicle, which is provided with the hydraulic functions, drives in a street. When, for example, this vehicle is equipped with a mobile crane, it is under no circumstances permitted to operate this crane during the drive.